People frequently wear hearing protection when they are in loud or noisy environments. Hearing protection can reduce the amount of noise the user's ears are exposed to. In some cases the user might want to hear some noises, such as a conversations or commands from people around them, music, other entertainment or other communication (e.g. AM/FM radio transmissions, Bluetooth transmissions, or communication from other transceivers) delivered through an input sound source. If the user is wearing hearing protection, hearing these desirable noises can be difficult or impossible. Therefore, there is a need to allow the user of hearing protection to still be able to hear some external noises, while still reducing the loud or undesirable noises.
Hearing protectors often require power to operate the apparatus. Batteries are often used to power these products. Users of hearing protection products can appreciate the convenience of using different battery types in the same apparatus. However, the different form factors of rechargeable batteries compared to standard cylindrical batteries often makes it difficult for a single apparatus to be powered by either type of battery without modifications that change the appearance and/or size of the apparatus. For safety reasons, it is also desired that products which can use rechargeable batteries have a means of preventing charging from occurring if a non-rechargeable battery or wrong type of rechargeable battery is used in the apparatus.